Electrical insulation



Patented July 1929.

WILLIAM F. DOERFLINGER, OF WEST NEW BRIGHTON, NEW YORK.

ELECTRICAL No Drawing.

This invention relates particularly to dielectric substances and toelectrical devices, such as transformers, oil switches and the like, inwhich conducting bodies differing in electrical potential are separatedby a dielectric liquid. p

It is' desirable that the liquid insulating medium or die'letric, insuch devices, combine'inhigh degree high dielectric strength,

freedom from moisture, acid and alkali etc., low evaporation loss forprolonged periods, high flash point, highburning point, small afiinityfor water, and smalltendcncy to form carbonaceous deposits or otherwisedecom- .15 pose. A considerable fluidity (or low viscosity) is alsooften of in'iportance.

Various materials, such as hydrocarbon oils, rosin oils, vegetable oils,etc., have been used for this purpose.

I have found that tricresyl phosphate is more suitableas a. dielectricliquid than most substances which have been proposed for this purpose.

Tricrcsyl phosphate is an odorless, colorless liquid, neutral incharacter, non-hygroscopic, and immiscible with water, has a high flashpoint and is substantially non-volatile and nonburnable. It is freelyfluid and has a high dielectric strength. It is very 3 stable.

Q 'I have found the dielectric strength tested between one inch discelectrodes spaced onetenth inch apart in accordancewith A. S. T. M.Specification D. 117 24 entitled Standard method of testing transformerand switch 0ils,using a transformer rated at 125 K. V., "25 K. V.Arsupplied with current at 120 volts 60 cycles is- Application fil edJune 22,

about 13,700 volts'at puncture, I

INSULATION. I

1928. Serial No. 287,652.

using ordinary good commercial material without special drying or othertreatment. 40 v I The'flash point is about 460 F. and the burning pointabout 705 F. It can be made to burn only with extreme difficulty.

The high burning point of tricresyl phosphate is of great importance inclosed transformers of large size; also its fluidity, which is ratherremarkable for a substantially nonvolatile liquid. This enables it toconvey away heat generated in the transformer very efliciently, andreadily self heat in case of a discharge. 7 j My invention is notconcerned with the elee- 'trical construction of transformers, switchesetc. In practicing it I merely use tricresyl phosphate in place of thehydrocarbon oils 5 etc. which are at present employed in apparatus ofthis type, such' as oil insulated trans-- formers. I i

What I claim is I e 1. An electrical device comprising ,conduc- '60 torsadapted in use to have different electrical potential, separated by adielectric comprising',tricresyl ph0sphate.-

2. An electr cal device usinghquid 1nsu lation including"a dielectriccomprising tricresyl phosphate. j

3. An electrical device using insulation consisting of tricresylphosphate, substantially as and for the purpose described. 4;. Anelectric device using insulation con- 7 sisting of'liquid tricresylphosphate,

5. An electrical device comprising conduc tors separated by liquidtricresyl phosphate.

This specification signed this 20th day of June,'1928. I 1 a WILLIAM F.DOERFLINGER.

